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Sorry the title is supposed to read "CAM over pressure". I tried to edit it but couldn't...When you set up sizing dies on a press that cams over is it necessary to get a hard cam over to completely full length size a case,or will a lighter cam over feel accomplish the same results. In my mind I am thinking that as long as the ram is stopping dead enough against the die to initiate cam over it is enough,but I want to be sure. Thanks
I very seldom have my sizing dies (rifle) screwed in enough to have a hard cam over. I bump shoulders 0.001-0.002" and this usually occurs with the die slightly off the shellholder. I don't screw carbide pistol dies in to cam over because it can crack the carbide ring.
So...I guess I'm saying that I don't set my presses to cam over unless I need it to bump the shoulder 0.001-0.002"
Brad
I measure fired cases with a comparator to get a number/measure of shoulder distance and set the die up in the press to so that the shoulder gets slightly bumped. That number being 0.001-0.002" less that the measurement of the fired case is all that matters.
I full length size most rifle brass so, I set it for a medium bump. I make sure on pistol dies with carbide rings that it doesn't contact the carbide. Some of them I've seen has the carbide recessed a bit so it doesn't touch.
Once the press cams over 0.001-0.002", more isnt moving the die anymore, just stressing the press.
The cam over is so you know that the press has gone the total distance; whereas, it starts going back down.
Cam over, is cam over; it is either camming-over, or it isn't. There isn't a "pressure" to it.
Thanks for the advice folks.
BK7 hit the nail on the head!. Not all dies and chambers are created equally.
Brand new 308 generally runs SAMMI -.003 to .004. I shoot it in my 308 and it grows to SAMMI + .004-.006. I neck size first time and it comes out after firing at +.007. I re-size bumping shoulder back to +.005-.006.
First firing case grows .009-.010
Second and subsiquent reloadiings .002
If is was to go to SAMMI 0.0
First time .010
Second .006-.007. (may not get full expansion) for each subsiquent reloading.
If I turn my die down to get hard contact I can get SAMMI -.002 on this body die. I've had a set of 223 dies that I could get SAMMI -.006.
Brass is not cheap as it once was and using premium brass is upward of 70 cents to 1.xx +. Do yourself a favor and get some shoulder datum point measuring g adapter for your calipers or borrow one from a friend set up for your brass. Measure some factory, once fired and your reloads and see what you get. Never had a problem with an AR or bolt chambering a round and locking. AR picking ammo is .002 under my smallest chamber. Match AR is .002 under that specific chamber.
If I re-si brass out of a 308 that is SAMMI 0.0 + .007 my cases grow quickly yet re-sizing
When you can see no daylight between the die and shell holder with a case inserted is as far as it's gonna go wether it's "camming " over at the bottom of the stroke or not is dependand on how you adjust your die
I don't cam over at all. I set my dies so the neck gets sized just shy of the shoulder. I like to just feel the bolt close on a loaded round as in .000 to -.0005 head space. Once the case grows to a slightly stiff bolt closing then screw the die down just enough to get a slight resistance on the bolt. Lock the die ring and leave it. Minimum amount of sizing, maximum case life. If it takes cam over to chamber a round, I trim the shell holder just a bit. I have a 308 I built that has -.005 head space on factory rounds to keep the resizing of new brass to a minimum. I don't want loaded rounds sloppy in the chamber nor do I want them stretching any more than necessary. This requires keeping the chamber and ammo clean so may not be for everyone.
The only time cam over would be necessary is if you brass was loaded so hot that you had case head expansion.
Correct. You don't want a 'hard' cam-over, it means you're doing something wrong.Quote:
Originally Posted by Elroy
Like Bk7 said. Sometimes you shouldn't cam over at all to full length resize. My brother recently did that for a newly acquired rifle and the result was excessive headspace. I size just enough so that a cartridge will chamber with slight resistance.
I appreciate all the good advice from you all..Quote:
Originally Posted by JSnover
The other presses I have owned were not cam over types. They just stopped dead,and I always set my dies at about a quarter turn down after they contacted the shell holder at full ram extension. I do the same on my new press,and it is too much. I realize the ram actually lowers slightly at the very end of the stroke, and that is were I was setting my dies as stated above, instead of at the maximum extension of the ram.
size the case, if it chambers easy your golden no need to stress the press or yourself.
Every die brand is different. It may seem obvious, but it seems too many skip reading the directions. I use Lee dies almost exclusively, and I set to cam over lightly. This normally bumps the shoulder back more than needed, but I have yet to have a die what I would consider excessive. Most Lee rifle dies seem to bump back to near maximum SAMMI specs. Normally I see .001"-.002" bump stated. While this is likely ideal for accuracy and case life, I've found that if you don't watch it, spring back can be a problem on these small amounts, especially with an expander ball die. Even sizing back .005"-.006", which is typical of a Lee die set to cam over, I have never had a case head separation.